1. Field of the Invention
The invention relates to a pressure regulating valve, having an electromagnet and a movable armature, that is used in particular in a fuel injection system for internal combustion engines for regulating a pressure in a fuel reservoir.
Electromagnets with a movable armature are also used as actuators in manifold applications.
2. Prior Art
Manifold versions of pressure regulating valves are known. The pressure regulating valve serves to regulate the pressure in a fuel reservoir, with which it communicates via an inlet. The pressure regulating valve has a pistonlike valve member, which is guided axially displaceably in a bore and which can move counter to a force that acts on the valve member, preferably by means of the current in the electromagnet. The force acts in the closing direction, so that the valve member is pressed onto a closing element of the pressure regulating valve and is pressed against a valve seat. The valve member forms an armature bolt of an electromagnet, which can be supplied with current to control the force.
By means of the current supply, a magnetic field is created, which penetrates the armature of the electromagnet and causes a magnetic force to act on the armature bolt. With this force, the valve member presses the closing element against the valve seat.
If the force generated by the hydraulic pressure of the fuel exceeds the closing force that is exerted on the closing element via the valve member, then the closing element is lifted from the valve seat. In this case, fuel flows out of the fuel reservoir through the inlet via the opened pressure regulating valve into a relief chamber.
When a higher pressure is set in the fuel reservoir, the current in the electromagnet is increased, so that the closing force is increased, and thus the closing element does not lift from the valve seat until at a higher pressure in the fuel reservoir, and then fuel can flow out of the fuel reservoir into the relief chamber.
3. Disadvantages Of The Prior Art
Regulating the pressure in the fuel reservoir is done via the setting of the current in the coil of the electromagnet. The actual pressure thus depends on the parameters of the electromagnet. These include not only the electromagnetic parameters but also the geometrical dimensions. The air gap between the movable armature and the fixed valve housing, within which gap the coil of the electromagnet is located, is of particular importance. The air gap is defined by the component geometry.
To enable adjusting the pressure precisely or regulating a precise pressure interval, the components must be adapted to one another precisely. The requisite manufacturing tolerances are correspondingly low, which means major assembly effort and hence expense.